The present invention relates to a control system for a turbocharger with a rotary electric machine or a motor-generator mounted on the rotatable shaft of the turbocharger.
Various proposals have been made to mount a turbocharger on the exhaust pipe of an internal combustion engine and couple a motor-generator to the rotatable shaft of the turbocharger for recovering the energy of exhaust gases emitted from the internal combustion engine.
Japanese Laid-Open Patent Publication No. 62-48932 discloses a proposed control device for a turbocharger combined with an internal combustion engine and associated with a motor-generator which can operate as a generator or a motor dependent on the rotational speed of and the load on the engine.
According to the proposed control device, when the motor-generator is operated as a generator, generated electric power is supplied to an electric load or a battery, and when the motor-generator is operated as a motor, it assists the turbocharger in supercharging the engine to increase the output power of the engine. However, the disclosed control device does not have a means for controlling the boost pressure of a turbocharger at an optimum boost level dependent on a change in the running conditions of a motor vehicle. Therefore, even under such running conditions for the motor vehicle to require quick acceleration, the boost pressure of the turbocharger may be too low to achieve desired acceleration when the accelerator pedal of the motor vehicle is depressed a full stroke.